From patchwork Thu Sep 7 04:26:07 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Cong Wang X-Patchwork-Id: 810846 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="aEdhOjgO"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3xnnTJ2fw2z9sNd for ; Thu, 7 Sep 2017 14:26:28 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753447AbdIGE01 (ORCPT ); Thu, 7 Sep 2017 00:26:27 -0400 Received: from mail-pf0-f194.google.com ([209.85.192.194]:38719 "EHLO mail-pf0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753374AbdIGE0S (ORCPT ); Thu, 7 Sep 2017 00:26:18 -0400 Received: by mail-pf0-f194.google.com with SMTP id q76so3986514pfq.5 for ; Wed, 06 Sep 2017 21:26:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=QP2ih+6R2zUU3QnYXeel7vXIeTgLdhbU/uqmelCoUag=; b=aEdhOjgOQv+XaymnOaES961LQcPjbCEvDrI/pe8Yj48jzluplhbaUs9ZsJwVrXVq3w hLM6hp6Iwc0Ae5VC5ET95qRUCvuI80DYKolzo6ZbH5R7ilnn+01Cm7T5Fdjs8yHrT9uO OslU69PkNEiPvPnp2PWR0BauCb5JBIi5wnkp9S98erm0aBmomR2CVCyxiEm4uw3qGQKV 0gJpm5lhZPGrKIfau08srencn49wqVWTYCqmIoXa3X0HrmpuAsHsU3rfToN7dqkPYJPJ Ip5L4OXa8KDN+PoOz+4Wn/tk3ZASEfvHbQ+DbcDLI+26TqkAUlX3oB/UBM+8pXNIILvB NobA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=QP2ih+6R2zUU3QnYXeel7vXIeTgLdhbU/uqmelCoUag=; b=G+AN0i/V9PDuhA6waY9YFwlqIVsgeJas3EGkmjq45EwEyfCO+ZfyVmDtNaiuAo+qNz ADrFO/3H3wUt+b7PvBu78d7FkLB8ZyYYE8Q55s7HbMiS7Hb1Bu1KpV+4W2Gpx1UQvjnb e7yQNlJPEeYmz6UcuzpVWCjHMGoOdaSgb5Xdr/asTV1IAJLx6NCzXWIBmUaiTK7M4nHO LaqKiyunE3nesV2E+UmAy8b94tdUiK0FMM2LfpmKujAt+TqbbookD/fHGk2vMx2+U9ji D2aBu2wAasbXWnnuDqNhmdlnyNEjU9mnUw+EMdsKOiWJ4PvspE/FfNeDqFpdKYX+u9KV s1xg== X-Gm-Message-State: AHPjjUgK9G7yYYYWOUb6KjzZrU3T2SsFYu31+OatXTWNhV9Tr5U3eGQ3 eb5nVAcHhcTXfUEkHgs= X-Google-Smtp-Source: ADKCNb5f0aqpHkgAO5RUrvV17ZKYec2Wguv3bAD4LVXcNnNM1Mr10YF2zIkdCn7n07j0DPq4aeA2CQ== X-Received: by 10.84.129.226 with SMTP id b89mr1571237plb.84.1504758377895; Wed, 06 Sep 2017 21:26:17 -0700 (PDT) Received: from tw-172-25-30-113.office.twttr.net ([8.25.197.25]) by smtp.gmail.com with ESMTPSA id i2sm1759997pfd.21.2017.09.06.21.26.16 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 06 Sep 2017 21:26:17 -0700 (PDT) From: Cong Wang To: netdev@vger.kernel.org Cc: jakub.kicinski@netronome.com, Cong Wang , Jiri Pirko Subject: [Patch net v2 2/2] net_sched: fix all the madness of tc filter chain Date: Wed, 6 Sep 2017 21:26:07 -0700 Message-Id: <20170907042607.24413-2-xiyou.wangcong@gmail.com> X-Mailer: git-send-email 2.9.4 In-Reply-To: <20170907042607.24413-1-xiyou.wangcong@gmail.com> References: <20170907042607.24413-1-xiyou.wangcong@gmail.com> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org This patch fixes the following madness of tc filter chain: 1) tcf_chain_destroy() is called by both tcf_block_put() and tcf_chain_put(). tcf_chain_put() is correctly refcnt'ed and paired with tcf_chain_get(), but tcf_block_put() is not, it should be paired with tcf_block_get() which means we still need to decrease the refcnt. Think it in another way: if we call tcf_bock_put() immediately after tcf_block_get(), could we get effectively a nop? This causes a memory leak as reported by Jakub. 2) tp proto should hold a refcnt to the chain too. This significantly simplifies the logic: 2a) Chain 0 is no longer special, it is created and refcnted by tp like any other chains. All the ugliness in tcf_chain_put() can be gone! 2b) No need to handle the flushing oddly, because block still holds chain 0, it can not be released, this guarantees block is the last user. 2c) The race condition with RCU callbacks is easier to handle with just a rcu_barrier()! Much easier to understand, nothing to hide! Thanks to the previous patch. Please see also the comments in code. 2d) Make the code understandable by humans, much less error-prone. Fixes: 744a4cf63e52 ("net: sched: fix use after free when tcf_chain_destroy is called multiple times") Fixes: 5bc1701881e3 ("net: sched: introduce multichain support for filters") Reported-by: Jakub Kicinski Cc: Jiri Pirko Signed-off-by: Cong Wang --- net/sched/cls_api.c | 38 ++++++++++++++++++++++---------------- 1 file changed, 22 insertions(+), 16 deletions(-) diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c index 6c5ea84d2682..e9060dc36519 100644 --- a/net/sched/cls_api.c +++ b/net/sched/cls_api.c @@ -209,21 +209,20 @@ static void tcf_chain_flush(struct tcf_chain *chain) RCU_INIT_POINTER(*chain->p_filter_chain, NULL); while ((tp = rtnl_dereference(chain->filter_chain)) != NULL) { RCU_INIT_POINTER(chain->filter_chain, tp->next); + tcf_chain_put(chain); tcf_proto_destroy(tp); } } static void tcf_chain_destroy(struct tcf_chain *chain) { - /* May be already removed from the list by the previous call. */ - if (!list_empty(&chain->list)) - list_del_init(&chain->list); + list_del(&chain->list); + kfree(chain); +} - /* There might still be a reference held when we got here from - * tcf_block_put. Wait for the user to drop reference before free. - */ - if (!chain->refcnt) - kfree(chain); +static void tcf_chain_hold(struct tcf_chain *chain) +{ + ++chain->refcnt; } struct tcf_chain *tcf_chain_get(struct tcf_block *block, u32 chain_index, @@ -233,7 +232,7 @@ struct tcf_chain *tcf_chain_get(struct tcf_block *block, u32 chain_index, list_for_each_entry(chain, &block->chain_list, list) { if (chain->index == chain_index) { - chain->refcnt++; + tcf_chain_hold(chain); return chain; } } @@ -246,10 +245,7 @@ EXPORT_SYMBOL(tcf_chain_get); void tcf_chain_put(struct tcf_chain *chain) { - /* Destroy unused chain, with exception of chain 0, which is the - * default one and has to be always present. - */ - if (--chain->refcnt == 0 && !chain->filter_chain && chain->index != 0) + if (--chain->refcnt == 0) tcf_chain_destroy(chain); } EXPORT_SYMBOL(tcf_chain_put); @@ -294,10 +290,18 @@ void tcf_block_put(struct tcf_block *block) if (!block) return; - list_for_each_entry_safe(chain, tmp, &block->chain_list, list) { + /* Standalone actions are not allowed to jump to any chain, and + * bound actions should be all removed after flushing. However, + * filters are destroyed in RCU callbacks, we have to flush and wait + * for them before releasing this refcnt, otherwise we race with RCU + * callbacks!!! + */ + list_for_each_entry(chain, &block->chain_list, list) tcf_chain_flush(chain); - tcf_chain_destroy(chain); - } + rcu_barrier(); + + list_for_each_entry_safe(chain, tmp, &block->chain_list, list) + tcf_chain_put(chain); kfree(block); } EXPORT_SYMBOL(tcf_block_put); @@ -375,6 +379,7 @@ static void tcf_chain_tp_insert(struct tcf_chain *chain, rcu_assign_pointer(*chain->p_filter_chain, tp); RCU_INIT_POINTER(tp->next, tcf_chain_tp_prev(chain_info)); rcu_assign_pointer(*chain_info->pprev, tp); + tcf_chain_hold(chain); } static void tcf_chain_tp_remove(struct tcf_chain *chain, @@ -386,6 +391,7 @@ static void tcf_chain_tp_remove(struct tcf_chain *chain, if (chain->p_filter_chain && tp == chain->filter_chain) RCU_INIT_POINTER(*chain->p_filter_chain, next); RCU_INIT_POINTER(*chain_info->pprev, next); + tcf_chain_put(chain); } static struct tcf_proto *tcf_chain_tp_find(struct tcf_chain *chain,